Edwards of Enfield developed a very successful extrusion puller powered by linear induction motors for application within the aluminium industry.
The puller takes advantage of the LIM thrust speed characteristic to exert a low-speed high-thrust pull on a gripper head. This gripper holds the end of the hot extrusion while the LIM applies controlled tension. As it is extruded from the hydraulic press the aluminium requires a constant tension to keep the 45m (150ft) extrusion straight and free from twist.
Once the puller has travelled its full length the gripper releases the metal. It then returns to the start of the line at high speed, at low thrust, grips a new piece of material, and the process is repeated indefinitely.
This development offered considerable improvement on previous drives;
Dangerous manual tensioning methods were eliminated
Dangerous high tension rope/chain pullers were eliminated
Operator safety was considerably increased
Automation improved productivity and profitability
Reliability was improved and maintenance reduced
Speed control was simple and cost effective
Between 300 and 400 puller systems have been installed world-wide, of which more than half were supplied by Force Engineering Ltd.
Several drive sizes and speeds were developed. The least powerful pullers up to 120kg (250lbs) using fan cooled LIMs whilst the more powerful ones up to 800kg (1750lbs) use water cooled units with on board closed-loop water cooling.
